1. Field of the Invention
The present invention relates to a method for managing defects which arise in an information recording medium, more particularly, to a method for creating/writing defect management information for an information recording medium, and to an apparatus and an optical disc using the method.
2. Description of the Related Art
Optical discs have come into wide use since the advent of CD (compact disc) and the demand for optical discs is expected to grow steadily with popularization of DVD (digital versatile disc). Optical discs include read-only discs such as CD-ROM and DVD-ROM, write-once discs such as CD-R and DVD-R, and rewritable discs such as CD-RW and DVD-RAM. Standard formats of CD-RW and DVD-RAM have released and standardization for VDR (video disc recorder) is in progress.
For rewritable optical discs such as DVD-RAM, defects which arise in their recording surface should be managed to achieve high reliable write/reproduction operation in a manner that data is not written to sectors in which read-out errors are detected beyond a predetermined level (hereinafter referred to as “defective” or “bad” sectors). To accomplish this, defect management is performed such that addresses of defective sectors are stored in a defect management table on the optical disc and data access to the defective sectors, write or read-out, is prohibited.
As shown in FIG. 1, the rewritable physical area of DVD-RAM has a lead-in area, a data area, and a lead-out area. The data area is divided into contiguous 24 groups, and guard area is situated before and behind each group. Each group is made up of a user area for recording data and a spare area which provides a storage area in place of defective portion of the user area.
The data area is also made up of a plurality of blocks, each of which consists of 16 sectors. The position of each sector is specified by a physical address which is given uniquely to each sector. When data is recorded, LSN (logical sector number) is assigned sequentially to every sector except defective ones.
Defect management information, or physical addresses of defective sectors within the data area are stored in DMA (defective management area), which is provided in four places, two in lead-in area and the other two in lead-out area, as shown in FIG. 1, to protect against the defects which may arise in the four DMA themselves.
The DMA is made up of two ECC (error correction code) blocks, or 32 sectors. The first ECC block consists of one sector for DDS (disc definition structure) and 15 other sectors for PDL (primary defect list). Sixteen sectors of the second ECC block are used for SDL (secondary defect list).
The examples of DDS, PDL, and SDL are illustrated in tables 1, 2, and 3, respectively.
TABLE 1DDS structureSizelocation(in byte)contents0˜12DDS identifier(0A0Ah)21Reserved (00h)31Disc Certificationflag4˜74DDS/PDL8˜92The number ofgroups 10˜20472038Reserved (00h)
TABLE 2PDL structureSizelocation(in byte)contents0˜12PDL identifier(0001h)2˜32The number ofentries in PDL4˜74The 1st bad sectoraddress 8˜114The 2nd bad sectoraddress.........
TABLE 3SDL structureSizelocation(in byte)Contents0˜12SDL identifier(0002h)2˜32Reserved (00h)4˜74SDL update counter 8˜158Spare area full flags16˜216Reserved (00h)22˜232The number of entriesin SDL24˜318The 1st bad sectoraddress & the 1streplacement sector address.........
Methods for creating and managing defect management information such as PDL and SDL are explained below with reference to DVD-RAM.